1. Field of the Invention
The present invention relates to skis in which one or several additional masses of inertia are added to modify and adjust the moment of inertia of the ski, both about a vertical axis and about a horizontal axis, which is perpendicular to the longitudinal direction of the ski.
2. Description of Background and Relevant Information
The moment of inertia about the vertical axis or rotation axis of the ski influences the performance of the ski in rotation, by determining the resistance of the ski to a variation in the direction of movement. A ski with a low moment of inertia, for example a short ski or a ski that is light at its ends, is easier to turn than a ski with a high moment of inertia. A ski that is easy to turn is particularly suitable for special snow conditions, such as deep snow, springtime snow, and for special terrain conditions, such as slopes with moguls. A ski with a high moment of inertia, for example an elongated ski or a ski having relatively significant masses at its ends, is particularly consistent when turning during a rapid descent, because the forces exerted laterally on the ski by the unevenness of the slope are better absorbed because of the higher moment of inertia.
The moment of inertia of the ski about its central horizontal axis which is perpendicular to the longitudinal direction of the ski influences the vibratory behavior of the ski. It is known that vibrations can be detrimental and can lead to the edges of the ski losing adherence with the ground, and, as a result, instability when turning.
Moreover, modern ski construction techniques are directed to lighter and lighter ski structures, which comprise, for example, a central core of light cellular material, surrounded by a structure of mechanical resistance in a casing. The lightness of such a structure leads to a substantial decrease in the moment of inertia and introduces the above-mentioned defects. It is known that such defects can be corrected by attaching additional masses of inertia to the ski.
In German Patent No. 2,052,332, the moment of inertia of a ski is modified by displacing masses in the direction of its length and fixing the masses on or within the rear or front portion of the ski. By modifying the distance of the masses from the two ends of a ski, the moment of inertia of the ski can be varied, both about the vertical axis and about the central horizontal axis which is perpendicular to its longitudinal direction. The practice of this system is however very difficult and expensive. The positioning of masses on the outside of the ski cannot practically be used because snow can accumulate in the adjustment elements and prevent their functioning. The positioning of masses within the ski unfortunately weakens the section of the ski, and requires the construction of entirely new skis having a hollow section for the masses and the displacement elements. Moreover, it appears that it is not possible to position such an .adjustable structure -for additional masses of inertia in the areas to obtain a satisfactory result, because these areas have too little thickness to receive the displacement elements for the masses of inertia. Satisfactory placement in these areas is the object of the present invention, and will be described in detail below.
French Patent No. 2,382,245 discloses positioning additional masses of inertia on the upper surface at the two ends of the ski. This document does not disclose the positioning of masses of inertia in particular areas to obtain the appropriate effect, as will be described below.